OnWindowCreated()

public class MyWindowAddOn : AddOnBase
{
    private NTMenuItem myMenuItem;
    private NTMenuItem existingMenuItem;
    protected override void OnStateChange()
    {
        if (State == State.SetDefaults)
        {
            Description = "Our custom MyWindow add on";
            Name       = "MyWindow";
        }
    }
    // Will be called as a new NTWindow is created. It will be called in the thread of that window
    protected override void OnWindowCreated(Window window)
    {
        // We want to place our add on in the Control Center's menus
        ControlCenter cc = window as ControlCenter;
        if (cc == null)
            return;
        /* Determine we want to place our add on in the Control Center's "New" menu
         Other menus can be accessed via the control's Automation ID. For example: toolsMenuItem,   
         workspacesMenuItem, connectionsMenuItem, helpMenuItem. */
        existingMenuItem = cc.FindFirst("ControlCenterMenuItemNew") as NTMenuItem;
        if (existingMenuItem == null)
            return;
        // 'Header' sets the name of our add on seen in the menu structure
        myMenuItem = new NTMenuItem { Header = "My Menu Item",
            Style = Application.Current.TryFindResource("MainMenuItem") as Style };
        // Place our add on into the "New" menu
        existingMenuItem.Items.Add(myMenuItem);
        // Subscribe to the event for when the user presses our add on's menu item
        myMenuItem.Click += OnMenuItemClick;
    }
    // Open our add on's window when the menu item is clicked on
    private void OnMenuItemClick(object sender, RoutedEventArgs e)
    {
        // Show the NTWindow "MyWindow"
        Core.Globals.RandomDispatcher.InvokeAsync(new Action(() => new MyWindow().Show()));
    }
}